Isomorph Invariance in the Liquid and Plastic-Crystal Phases of Asymmetric-Dumbbell Models

Eman Attia, Jeppe Dyre*, Ulf Rørbæk Pedersen

*Corresponding author

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review


: We present a numerical study of the asymmetric dumbbell model consisting of “molecules”
constructed as two different-sized Lennard-Jones spheres connected by a rigid bond. In terms of
the largest (A) particle radius, we report data for the structure and dynamics of the liquid phase for
the bond lengths 0.05, 0.1, 0.2, and 0.5, and analogous data for the plastic-crystal phase for the bond
lengths 0.05, 0.1, 0.2, and 0.3. Structure is probed by means of the AA, AB, and BB radial distribution
functions. Dynamics is probed via the A and B particle mean-square displacement as functions of
time and via the rotational time-autocorrelation function. Consistent with the systems’ strong virial
potential-energy correlations, the structure and dynamics are found to be isomorph invariant to a
good approximation in reduced units, while they generally vary considerably along isotherms of the
same (20%) density variation. Even the rotational time-autocorrelation function, which due to the
constant bond length is not predicted to be isomorph invariant, varies more along isotherms than
along isomorphs. Our findings provide the first validation of isomorph-theory predictions for plastic
crystals for which isomorph invariance, in fact, is found to apply better than in the liquid phase of
asymmetric-dumbbell models.
Udgave nummer4
Sider (fra-til)388-403
Antal sider16
StatusUdgivet - 9 nov. 2022


  • asymmetric-dumbbell models
  • plastic crystals
  • isomorph theory
  • hidden scale invariance

Citer dette